Depth like the height the depth needs extra consideration.
Minimum garage door height for pontoon boat.
But you might want 26 or 28 to handle 20 24 ft boats.
One thing is to see what size boats are common in your area and that are stored at home and not at a marina or boat yard.
The majority of the garage plans with boat storage in this collection feature at least one bay that is 28 deep nicely handling a boat and trailer.
Modern pontoons are often longer than their stated size.
Just the cost to raise the door height on my storage garage which is a post frame building was prohibitive and that is just metal and because the ceiling was built to accommodate a 7 foot door not an 8.
Driveway pitch check the angle of the driveway in front of the garage.
If it is angled up that may throw off your measurements about clearing the overhead door.
That would be a lot of work to modify that to accept an 8 foot garage door especially with the masonry work that would need to be performed.
I think that a 24 deep garage would hold an 18 ft boat with standard trailer.
Some of these designs offer taller ceilings and oversized garage doors for convenience.
With this kind of width and height dimension you would need garage of around 12 feet width and 12 feet of height door.
But even with the smaller trailers the dimensions you would need for garage of at least 10 feet width and 10 12 feet height.
The bow of the boat clears the door about 18.
Travel trailer also come in smaller sizes and they may need smaller door.
As a rule of thumb you should have at least a foot of clearance for safe movement and storage when you back the trailer and boat back in to the garage.
A 24 pontoon might be 25 9 length overall.
If your boat is above a certain height you need a permit to tow it.
The engine might extend a couple foot behind the length of the boat.
A baha 299 30 boat would fit nicely under a 14 height.